1. Field of the Invention
The present invention relates to rotary fans, and particularly to rotary fans incorporating blades of various sizes and locations.
2. Prior Art
Electronic devices such as central processing units (CPUs) frequently generate large amounts of heat during normal operation, which can destabilize operation and cause damage. Oftentimes, a heat dissipation assembly is used to dissipate heat from the electronic device. The heat dissipation assembly frequently comprises a fan facilitating heat dissipation from the electronic device.
Referring to FIG. 4, a conventional fan 1 comprises a central hub 2 and a plurality of spaced blades 3 radially extending from the hub 2. The blades 3 are all isometric and evenly spaced apart. Sizes of the blades 3 depend on a required power of the fan 1. A natural frequency of such blades 3 is therefore constant. Unfortunately, the natural frequency of such blades 3 is sometimes close to or within a range of the working frequency of a corresponding heat dissipation assembly. Resonance is produced, which results in extra noise and vibration.
The resonance problem can be overcome by using heavier blade material to increase the natural frequency of the blades beyond the range of the working frequency of the heat dissipation assembly. This expedient, however, increases a weight of the fan and increases costs.
It is strongly desired to provide an improved fan which overcomes the above problems.
Accordingly, an object of the present invention is to provide a fan which has non-uniform blades that render a natural frequency of the blades beyond a range of a working frequency of a corresponding heat dissipation assembly.
To achieve the above-mentioned object, a fan in accordance with a preferred embodiment of the present invention comprises a central hub, and a plurality of spaced and substantially sector-shaped blades radially extending from the central hub. The blades surround the central hub. Shapes of the blades are similar. Sizes of the blades are all different from one another. Spacings between any two adjacent blades are all different from one another. The blades can therefore be configured such that a natural frequency of the blades is outside a range of a working frequency of a corresponding heat dissipation assembly which is used to dissipate heat from a corresponding electronic device. Resonance of the blades can therefore be completely avoided. Noise and vibration of the blades when the fan is operated can therefore be minimized.
Other objects, advantages and novel features of the present invention will be drawn from the following detailed description of preferred embodiments of the present invention with attached drawings, in which: